Internal combustion engine and camshaft thereof

ABSTRACT

Cams are formed on a camshaft that correspond to intake valves so that intake flow of an internal combustion engine may be improved. The cams each have a cam lobe and the lobes of different cams are formed in different shapes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of Korean Application No.10-2003-0074756, filed Oct. 24, 2003, the disclosure of which isincorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an internal combustion engine and astructure of a camshaft for the internal combustion engine. Morespecifically, the engine and camshaft structure are capable of improvingthe flow of intake entering into a cylinder.

BACKGROUND OF THE INVENTION

Internal combustion engines are widely used. The engines often employ aplurality of intake valves in each cylinder. Intake valves of aninternal combustion engine are driven by a camshaft, and morespecifically, the intake valves are driven by a cam formed on thecamshaft.

Operation timing and pattern of the intake valve are determined by thecam of the camshaft. Therefore, as multiple intake valves are driven,cams are formed on a camshaft following the number of intake valves inthe engine. Nevertheless, according to the available arts, the shape ofthe cam that drives the intake valves are identically formed. In otherwords, the intake valves that are arranged in a plurality in eachcylinder operate in the same operation and timing.

If flow of air, intake flow, that enters the engine through the intakevalves can be improved, complete combustion and output power of theinternal combustion engine can be improved.

SUMMARY OF THE INVENTION

According to a preferred embodiment, a camshaft structure for aninternal combustion engine includes a plurality of cams. The pluralityof cams include a first and a second cam to individually drive a firstand a second intake valve, respectively, arranged for a single cylinder.The first and the second cam lobes of the first and second cams areformed in different shapes.

It is preferred that the first and second cam lobes have a principalaxes offset from each other in terms of their offset angle settings. Itis also preferable that the offset angle is an angle of less than about60 degrees.

Preferably, the internal combustion engine of the present invention isan internal combustion engine that includes at least one cylinder andincludes a first and a second intake valve that are arranged for onecylinder and a camshaft that is provided with a plurality of cams,including at least a first and a second cam to individually drive thefirst and second intake valves, respectively. The first and second camlobes of the first and second cams are formed in different shapes. It ispreferable for the first and second cam lobes have a principal axesoffset from each other in terms of their offset angle settings. It isalso preferable that the offset angle is an angle of less than about 60degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding of the nature and objects of the invention,reference should be made to the following detailed description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a camshaft according to anembodiment of the present invention taken along line I-I of FIG. 2;

FIG. 2 is a cross-sectional view of an internal combustion engineshowing a camshaft according to an embodiment of the present inventionemployed therein; and

FIGS. 3-5 illustrate a beginning period of an intake stroke, a middleperiod of an intake stroke, and a final period of an intake stroke,respectively, of an engine following revolution of a camshaft accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows a cross-section of an internal combustion engine 200 with acamshaft 100 disposed within the engine 200 and FIG. 1 shows an axialview of a cross-section of the camshaft 100 of FIG. 2 taken along lineI-I. As shown in the FIGS. a cylinder block 250 and a cylinder head 260are combined to form a cylinder 205 of the engine 200. A plurality ofintake valves, for example, a first and a second intake valve 210, 220are respectively arranged in a first and a second intake port 261, 262of the cylinder 205.

According to an embodiment, the camshaft 100 is furnished with a firstand a second cam 110, 120. The first and second cams, 110 and 120, drivethe first and second intake values 210, 220, respectively. Furthermore,the first and second cams 110, 120 have their first and second lobes115, 125 formed in different shapes. More specifically, as illustratedin FIG. 1, the first and second cam lobes 115, 125 are formed such thattheir principal axes 112, 122 are offset from each other in terms oftheir offset angle (θ) settings. Such an offset angle (θ) may be clearlyset by a person of ordinary skill in the art depending upon the intendedintake inflow. However, according to an embodiment, it is desirable thatthe offset angles (θ) of the first and second cam lobes 115, 125 isformed to be less than about 60 degrees.

According to FIG. 2, the internal combustion engine 200 is provided withat least one cylinder 205 while the first and second intake valves 210,220 are arranged in the cylinder (205). The camshaft 100 is installed inthe top of the first and second intake values 210, 220. The first andsecond cams 110, 120 formed on the camshaft 100 drive the first andsecond intake valves 210, 220, respectively.

An exemplary process of intake flow generated within a cylinderfollowing revolution of the camshaft 100 in the internal combustionengine 200 according to an embodiment of the present invention is shownin FIGS. 3-5. More specifically, FIG. 3 shows an intake flow generatedin the beginning period of an intake stroke in the internal combustionengine 200 utilizing an embodiment of the present invention. FIG. 4shows an intake flow generated in the middle period of an intake strokein the internal combustion engine 200 utilizing an embodiment of thepresent invention. And, FIG. 5 shows an intake flow generated in thefinal period of an intake stroke in the internal combustion engine 200utilizing an embodiment of the present invention. FIGS. 3 b, 4 b, and 5b are top views schematically illustrating the cylinder 205, intakevalves 210, 220, and exhaust valves 310, respectively. While FIGS. 3 a,4 a, and 5 a are cross-sectional views of FIGS. 3 b, 4 b, and 5 b takenalong lines III-III, IV-IV, and V-V, respectively.

In the beginning period of an intake stroke, as illustrated in FIG. 3 a,the first cam 110 first drives the first intake valve 210 by revolutionof the camshaft 100. Therefore, the first intake valve 210 opens first,as illustrated in FIG. 3 b, such that intake flow in a clockwisedirection takes place in the beginning period of the intake stroke. Inthe middle period of the intake stroke, as illustrated in FIG. 4 a, thefirst and second cams 110, 120, respectively drive the first and secondintake valves 210, 220 by revolution of the camshaft 100. As a result,the first and second intake valves 210, 220 become open at the similarextents so intake flow is either slight or not formed in the middleperiod of the intake stroke, as illustrated in FIG. 4 b. In the finalperiod of the intake period, as illustrated in FIG. 5 a, drive of thefirst intake valve 210 by the first cam 110 is terminated by revolutionof the camshaft 100, and drive of the second intake valve 220 by thesecond cam 120 becomes in a maintained state. Therefore, only the secondintake valve 220 becomes open so intake flow in a counterclockwisedirection takes places in the final period of the intake period, asillustrated in FIG. 5 b.

Preferred embodiments concerning the present invention are described inthe above. However, this invention is not intended to be limited to thedescribed embodiments, but include all modifications and alterations aswill be appreciated by one of ordinary skill in the art that fall withinthe scope of the appended claims.

According to embodiments of the present invention, operation timing ofthe first and second intake valves arranged such that intake flow of airsucked into a cylinder may be improved. Therefore, since degrees ofmixing of air and fuel may be improved in a cylinder, contributions maybe made to complete combustion, reduction of harmful exhaust gas, andimprovement of output of an internal combustion engine.

1. A camshaft structure for an internal combustion engine, comprising: aplurality of cams including a first and a second cam to respectivelydrive a first and a second intake valve arranged for a cylinder, whereinfirst and second cam lobes of said first and said second cams are formedin different shapes.
 2. The camshaft structure according to claim 1,wherein said first and second cam lobes are offset from each other ontheir principal axes by their offset angle settings.
 3. The camshaftstructure according to claim 2, wherein said offset angle is less thanabout 60 degrees.
 4. An internal combustion engine, comprises: at leastone cylinder; at least a first and a second intake valve arranged forsaid one cylinder; and a camshaft provided with a plurality of cams thatinclude a first and a second cam to respectively drive the first and thesecond intake valves, wherein first and second cam lobes of said firstand second cams are formed in different shapes.
 5. The internalcombustion engine according to claim 4, wherein said first and secondcam lobes are offset from each other on their principal axes with theiroffset angle settings.
 6. The internal combustion engine according toclaim 5, wherein said offset angle is less than about 60 degrees.
 7. Acamshaft for an internal combustion engine, comprising: a generallylinear shaft having a length and a width; and at least two intake camscoupled with said generally linear shaft, said at least two intake camsconfigured and dimensioned to operate independent intake valves of aparticular cylinder, wherein said at least two intake cams include camlobes and said cam lobes are of different shapes from each other.
 8. Thecamshaft of claim 7, wherein said different shape is an offset ofrotation about a longitudinal axis of said generally linear shaft. 9.The camshaft of claim 8, wherein said offset is about 60 degrees orless.
 10. The camshaft of claim 7, further comprising a plurality ofintake cams configured and dimensioned to operate a plurality ofindependent intake valves of the particular cylinder.